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PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 173 
The Kennebunkport rock is a coarse, dull-gray granite, in which the 
feldspar is nearly all orthoclase and very impure and muddy. The small 
cavities in the quartz are very abundant. Biotite occurs only in small, 
very ragged shreds, often altered into a greenish product, and bearing 
numerous irregular inclosures of yellowish-green epidote. Sphene 
abounds in well-defined wedge-shaped crystals, which stand out in bold 
relief from the surface of the section. Apatite, zircon, and magnetite 
are present in small scattering crystals. The stone works well and 
takes a good polish. Its principal markets are the larger cities in Maine 
and New Hampshire. 
Very many of these biotite granites contain numerous masses or 
nodules of a darker color and finer texture than the rock itself, they 
frequently appearing as black patches on a polished surface. ‘These 
are of all sizes up to a foot in diameter. They sometimes occur with 
sharp, distinct outlines, or again merge gradually into the surrounding 
rock with no definite line of demarkation. Some of them possess a 
fine, even texture, while others are rendered slightly porphyritic in 
structure through included erystals of plagioclase of considerable size. 
Under the microscope they are all found to consist essentially of the 
same minerals as the rocks in which they occur, although in a more 
finely erystalline state and different proportions; biotite usually pre- 
vails and causes the dark color of the patch. Very many of them, how- 
ever, are penetrated in every direction by innumerable, minute, color- 
less, needle-like crystals, an exact determination of which, on account 
of their small size, is impossible. Many of the included larger crystals 
of feldspar, which, so far as observed, are always triclinic, have their 
angles rounded away, and are reduced to mere oval grains. Such nod- 
ules are usually regarded as of concretionary origin.* The finer texture 
and darker color of these patches render them very conspicuous, and in 
some of the quarries many fine blocks of granite are rendered entirely 
unsuited for finely finished or polished work on account of their abun- 
dance. 
Hornblende granite.—This is rather a rare building-stone in Maine, 
though extensively quarried in other States. Its production is at pres- 
ent confined to Otter Creek, Mount Desert, where a beautiful coarse 
red rock is quarried, which on a superficial examination somewhat resem- 
bles the biotite granites of Calais and Jonesborough, though lacking the 
cream-colored feldspar and consequent speckled appearance character- 
istic of these rocks. Orthoclase predominates over all other constitu- 
ents, and is deep-red in color. Under the microscope the feldspars 
are so opaque that their optical properties can be determined only ap- 
proximately. The hornblende occurs in small broken fragments and 
* See “‘On Concretionary Pat¢hes and Fragments of other Rocks contained in Gran- 
ite,” by J. A. Phillips, Quarterly Journal of the London Geological Society, Vol. 
XXXVI, 1880, pp. 1-22. Also, ‘‘On the Black Nodules in the Maine Granites,” by 
G. P. Merrill, this vol., p. 137. 
